This application claims priority upon German application 197 47 949.9 filed Oct. 30, 1997, which is incorporated herein by reference.
The invention relates to a device for setting the length of a top link of a tractor attaching device. The attaching device, apart from a top link, also includes two lower steering arms. The two lower steering arms are arranged so as to be laterally displaced from the longitudinal axis of the tractor and are articulatably attached at one end. The top link has a power drive which is used for length setting.
A publication entitled xe2x80x9cHydraulic Top Link with Hookxe2x80x9d of GKN Walterscheid GmbH, Lohmar, Germany (TAS 156/I D/GB/F 996 G10-I 309562) describes a top link with a hydraulic cylinder used as a power drive. It has a double-acting piston-cylinder unit with a twin return valve (double check valve). The valve serves to block the set length even in the case of longer periods of rest A marking rod is also provided, which facilitates handling.
Achieving the optimum length setting for the top link when the tractor operates with an attached implement requires considerable experience. The operative always has to carry out a manual operation to adapt the length setting. This is labor-intensive and optimum kinematic conditions for the respective implement are not achieved.
It is an object of the present invention to provide a device which achieves optimum kinematics in operation for each attached implement.
In accordance with the invention, a device for setting the length of a top link forms part of an attaching device of a tractor. A displacement sensor is provided which records the respective actual length setting of the top link. The sensor generates an electric actual length signal which represents the actual length setting. A lift position sensor is present to generate an electric signal which represents the actual lift position of the lower steering arms. A storage unit is present to store a nominal length setting of the top link. The nominal length setting relates to the respective actual lift position. When a new actual lift position is reached, the storage unit generates an electric control signal corresponding to the nominal length signal. The control unit actuates the power drive as a function of the deviation of the respective actual length setting from the control signal.
An advantage of this embodiment is that the respective kinematics meet greatly differing requirements. The operative is offered specific functional improvements and greater comfort. It is possible to achieve kinematics which are adapted to a specific implement. The required predetermined values may be entered by hand It is also possible to enter into the storage unit a specific tractor/implement combination in the form of a special program.
According to a further embodiment, the respective nominal length settings relative to the associated lift positions can be stored in the storage unit in the form of a curve. In this context, the two end points of the curve are stored in the storage unit by moving to the highest lift position, in combination with a first nominal length setting and, respectively, to the lowest lift position, in combination with a second nominal length setting of the top link with the implement connected to the attaching device. This means that the end points of the curve can be adapted for each tractor/implement combination. For most applications, the curve may be presented by a straight line extending between the end points. However, it may also be necessary to store a special curve. The decisive factors are the two end points which are stored by a so-called xe2x80x9cteach-inxe2x80x9d method. Accordingly, while the end positions are stored, it is also possible to store intermediate positions between the two end positions. The intermediate positions may be individually stored. The intermediate positions are created by lifting the lower steering arms to a first position, then manually adjusting the top link to a position so that the implement attached to the lower steering arms and the top link assumes the first position. Thus, this given lifting position of the lower steering arms is stored as an intermediate position. This process may be carried out to produce additional intermediate positions.
The invention can be complemented by arbitrarily changing the curve by changing the length setting of the top link. Thus, a curve is obtained with a discontinuity from which two straight lines are assumed to extend to the end points. Finally, it is possible to store curves for several different implements in the storage unit. Thus, the curves may be activated when the respective implement is connected to the attaching device.
In a preferred embodiment, the power drive for the top link is a hydraulically loadable piston/cylinder unit. The control unit is preferably a microprocessor. It is possible to select different operational conditions. Thus, the respective nominal length setting for the top link represents a function of the lift position of the lower steering arms.
The control means permt different operational conditions which can be determined, for instance, by an operation selection switch. In a first position, for instance in the xe2x80x9coffxe2x80x9d position, the control unit is deactivated and the length of the top link cannot be changed. In a second selectable position, the xe2x80x9cautomaticxe2x80x9d position, it is possible to automatically control the length of the top link as a function of the position within control range limits. Outside the control range limits, the length remains constant.
A third type of operation exists, the xe2x80x9cfloating positionxe2x80x9d. This position differs from the automatic type of operation in that the length between the control range limits is not controlled. The power drive of the top link is disconnected. Furthermore, a xe2x80x9cmanualxe2x80x9d type of operation is possible. Here, the length of the top link is set by hand. In this case, the power drive is controllable by hand, so that any kind of setting is possible.
Further, in the xe2x80x9cautomaticxe2x80x9d position and in the xe2x80x9cfloatingxe2x80x9d position, it is possible to superimpose manual operation. This permits temporary adjustments, for instance, changing the angle of attack of the working tool. Finally, it is possible, in addition to manual control facilities, to provide remote control means. This permits control by radio or by a cable connection. These control means permit the most varied requirements to be met by the kinematics. The user benefits from specific functional improvements and greater comfort
From the following detailed description, taken in conjunction with the accompanying drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.